They tightened measures after the junta crushed protests led by Buddhist monks two years ago, killing at least 31 people.
Thein Sein met in New York with US Senator Jim Webb, a strong advocate for a new course on Myanmar, who paid a rare visit to the country last month.
Webb hailed the new policy on Myanmar as a signal “that we have the potential to change the dynamic of this important relationship.”
Campbell said that the US would talk to Myanmar about elections scheduled next year, but for the time being was “skeptical” about the vote.